This invention relates to hydrodynamic bearings for vibratory mechanisms, and more particularly to the use of hydrodynamic journal bearings as the primary support for the eccentric apparatus of industrial-type vibratory mechanisms.
At the present time vibratory mechanisms are utilized throughout industry to perform a wide variety of functions, such as consolidation of loose materials; loosening, separation and moving of particulate matter; reduction of particle size; and various machining, forming, finishing and surface treatment operations. For example, a vibration finishing machine includes a tub adapted to receive piece parts to be finished and a media which may comprise metal, glass, ceramic, plastic, wooden or composite materials, and which may take the shape of balls, cones, discs, cylinders, triangles, stars, pyramids, polyforms, and random shapes. The tub also receives a liquid such as water and may receive a finishing agent. The tub is supported for vibration and eccentric apparatus is utilized to impart vibratory energy to the tub and the contents thereof. By this means the piece parts and the media in the tub are actuated to move in a tumbling or rolling pattern which together with the vibration caused by the operation of the eccentric apparatus causes the media to perform the desired finishing operation on the piece parts.
The eccentric apparatus of commercially available vibratory machines usually comprises either a rotatably supported shaft having eccentric weights mounted thereon or an eccentric shaft. In either case the shaft of the eccentric apparatus utilized in present vibratory mechanisms is typically supported by means of antifriction bearings, such as ball bearings, roller bearings, or tapered roller bearings. Although antifriction bearings are presently utilized almost universally as the eccentric apparatus support in vibratory mechanisms, the use of such bearings for this purpose has been found to involve two distinct disadvantages. First, antifriction bearings involve the use of rolling components in contact with non-rolling components. As the speeds and radial loads on such bearings are increased, this contact results in the generation of extreme localized heating. This heating is detrimental to the bearing components in that the heat treated surfaces are reduced in hardness and eventually fail. Second, the bearing components are subjected to repeated tensil, compressive, and torsional loads. Even though the components may not be stressed beyond their elastic range, this periodic loading eventually causes fatigue which leads to bearing failure. These and other factors result in relatively rapid bearing failure in presently available vibratory mechanisms, and in fact one of the most persistent problems that is encountered in the use of such devices is the frequent necessity of replacing the bearings which support the eccentric apparatus.
In attempting to overcome the foregoing and other difficulties long since associated with the use of antifriction bearings in vibratory mechanisms, it has been proposed to support the eccentric apparatus of such mechanisms by means of hydrodynamic bearings. As is well known to those skilled in the art, such bearings are characterized by a thin film of lubricant between the relative moving parts, whereby no actual contact between the parts occurs. By this means all problems involving possible fatigue of the component parts of the bearings are eliminated. Moreover, by controlling the temperature of the lubricant it is possible to eliminate problems involving localized excessive heating of the component parts of such bearings.
It has been found, however, that the mere substitution of journal bearings for antifriction bearings as the support structure for the eccentric apparatus of a vibratory mechanism does not provide an operable result. To the contrary, it has been found that such a substitution leads to rapid wear and often to catastrophic failure of the journal bearing structure. While this phenomenon is not completely understood, it is theorized that it is caused by misalignment of the rotating shaft with respect to the hydrodynamic bearings. It is believed that such misalignment causes localized depletion of the lubricant film between the shaft and the bearings, whereby the adjacent metal parts come into actual physical contact leading to rapid wear and localized heating, and ultimately to bearing failure.
In accordance with the present invention, the foregoing and other difficulties long since associated with the prior art are overcome, whereby the use of hydrodynamic bearings as the primary support for the eccentric apparatus of a vibratory mechanism is facilitated. In accordance with the broader aspects of the invention, a vibratory mechanism includes apparatus adapted for vibratory actuation to perform a predetermined function. A housing is connected to the apparatus and in turn supports hydrodynamic journal bearings. An eccentric apparatus includes a shaft which is rotatably supported in the journal bearings. Upon rotation of the shaft, the eccentric apparatus generates vibration which is transmitted through the journal bearings and the housing to the function performing apparatus. The shaft and the housing have matched deflection characteristics under the loads imposed by the eccentric apparatus, whereby the hydrodynamic journal bearings and the portions of the shaft extending therethrough are continuously maintained in precise alignment. By this means the vibratory mechanism is provided with substantially infinite bearing life.
In actual practice it has been found that the use of the present invention provides advantages in addition to substantially increased bearing life. Thus, by means of the invention it is possible to provide between about five and about ten times as much energy input to the mechanism as is possible when antifriction bearings are employed as the primary support for the eccentric apparatus. Simultaneously, it is possible to operate the eccentric apparatus between about two times and about four times as fast as is possible when antifriction bearings are employed. Both of these factors tend to dramatically improve the operating performance of a vibratory mechanism utilized in the present invention.